1. Field of the Invention
The present invention relates to an improved optoelectronics package which permits high frequency operation and couples rays from a light emitting semiconductor element for use in optical transmission to an optical fiber or vice versa.
2. Prior Art
An optoelectronics package comprising a laser diode (hereinafter abbreviated as "LD") as an optical semiconductor will be described hereinafter.
FIG. 4 is a partially sectional view illustrating the configuration of the prior art optoelectronics package. As shown in Fig. 4, LD 1 and lens 2 are carried by a metallic carrier 3 which is fixed to an airtight vessel 5 via an electronic cooling element 4. Electric wiring for driving LD 1 consists of two independent thin gold wires 7a and 7b. The wire 7a connects an input terminal 6a for receiving a driving signal to a terminal of LD1, and the wire 7b connects the other input terminal 6b, or ground terminal, to the other terminal of LD1 through the carrier 3. The input terminal 6a is electrically insulated from the vessel 5 by insulating glass material 8. Rays 9 from LD 1 are condensed by the lens 2 and go out from the vessel 5 through an aperture 10 which is mounted to the vessel 5 by low melting glass material 11.
The prior art optoelectronics package 12 having such a configuration is normally used in conjunction with an optical fiber 13 which is adjusted in position such that the rays 9 from LD 1 enter the fiber 13. Further, optical fiber 13 is fixed to the optoelectronics package 12 via a holder 14. The electronic cooling element 4 is configured such that a temperature difference is developed between its top surface touching the carrier 3 and its bottom surface touching the vessel 5. In this configuration, the electronic cooling element 4 has a cooling capability such that the temperature of the carrier 3 and LD 1 can be kept constant in spite of any fluctuation in the temperature of the vessel 5.
FIG. 5 is a simplified equivalent electric circuit of the optoelectronics package of Fig. 4. As shown in Fig. 5, the input terminal 6a and LD 1 are connected to each other via an inductance (L.sub.A) 15 of the gold thin wire. An Inductance (L.sub.B) 16 of the gold thin wire 7b and a capacitance (C.sub.P) 17, which is provided by the cooling element 4 as a stray capacitance, are connected in parallel between the input terminal 6b and LD 1. The equivalent electric circuit shown in Fig. 5 is a filter circuit in which the inductance (L.sub.B) 16 and capacitance (C.sub.P) 17 together produce a parallel resonance at a frequency fr ##EQU1## which gives a high impedance. Therefore, the prior art optoelectronics package is disadvantageous in that the amplitude and phase of the signal transmitted to LD 1 have a large degradation in the vicinity of resonance frequency fr, disabling a faithful transmission of signal.
In order to eliminate such a disadvantage, the inductance (L.sub.B) 16 or capacitance (C.sub.P) 17 may be reduced to raise the frequency range at which the effect of the above-described filter circuit is greatly produced so that such an effect is less pronounced in a frequency range commonly used in telecommunications. However, the capacitance (C.sub.P) 17 is inherent to the electronic cooling element 4 and therefore cannot be reduced. Inductance (L.sub.B) 16 may be reduced by decreasing the length of the wire 7b or increasing the diameter of the wire 7b. However, either approach is disadvantageous in that it causes an increase in the thermal inflow from the vessel 5 to the carrier 3, deteriorating the cooling capability of the electronic cooling element 4.